Re: Apple IIc expansion options

[dempson@actrix.gen.nz (David Empson)]

**** **** <***@***.com> wrote:

>     What are the expansion options available on the 2c?

Nearly all expansion options are external.

Applied Engineering did a memory expansion card which operates like the
RamWorks (multi-bank auxiliary memory).  This plugs into the CPU and MMU
sockets, and those chips then plug into the card.

Later revisions of the IIc have a dedicated memory expansion slot, for
Apple's IIc memory expansion card, which works like Apple's standard
slot RAM card for the II+/IIe, i.e. a "slinky".  The motherboard
contains all the firmware support - the card is almost purely RAM with
very little support circuitry required (probably one ASIC to implement
the "slinky" address latch).

You can also use a Zip Chip or Rocket Chip to accelerate the CPU.

The IIc+ has a modem slot, but I don't know if anything was ever made to
go in it.  It ties into the slot 2 hardware (making use of the existing
6551 on the motherboard), and I expect the external modem port would be
disconnected automatically if you plug in an internal modem.

> I'm somewhat familiar with what can be done externally, and I realize that
> there are no internal slots. Are these slots totally absent from the
> design, or are the sockets simply missing from the mainboard?

The motherboard hardware emulates the slots, in that you have I/O
devices and firmware which appear to be in slots 1-7 as far as the
software is concerned.  Most of the physical slot signals are missing.
For example, there are no IOSEL or IOSTROBE signals - the IIc uses a
single ROM that is enabled for all locations in $C100-$FFFF.  (The
"UniDisk" and later revisions also use bank switching to toggle the
entire ROM space between two 15.75 KB banks, to allow for extra code
like the SmartPort support and self-test.)

The DEVSEL signals probably exist in some form, since there are I/O
devices in the address space for slots 1, 2 and 6.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P O Box 27-103, Wellington, New Zealand